The present invention relates to a method for determining the tread depth of a vehicle tire while the vehicle is moving.
From German patent application 19 523 917 a method for determining the tread depth of a vehicle tire while the vehicle is moving is disclosed. Based on the measured values for the vehicle velocity and the measured values of wetness sensors, that detect the water spray caused by the tires when driving on a wet road surface, with the aid of a characteristic line field the tread depth of the vehicle tire is determined.
From German patent application 32 36 520 a method for detecting the tread depth of vehicle tires while the vehicle is driving can be taken whereby, based on the measured values of the rpm sensors at the wheels and on determined reference velocities, long term changes of the tire state (wear) and thus the actual tread depth are deduced.
From German patent application 195 14 219 a method for determining the tread depth of vehicle tires can be taken in which the momentary value of the tread depth is determined based on the initial tread depth PT.sub.0, a specific tire wear, which incorporates a driving behavior-proportional value SK1 determined continuously during driving by different sensors, and the driven miles.
From German Offenlegungsschrift 44 35 160 a device for determining the circumferential force of a vehicle wheel is known which functions without contacting the wheel. At least one first sensor element is provided in the sidewall of the tire which generates, when passing a sensor provided at the vehicle, a signal that is used for determining the angular position of an outer vehicle tire point relative to a hub-based coordinate system that rotates with the tire. The hub-based coordinate system is represented either by a second sensor and a second vehicle-attached sensor or by an ABS sensor of the vehicle mounted on the wheel hub.
It is therefore an object of the present invention to use the signal provided by the sensor for determining the tread depth of the vehicle tire while the vehicle is moving.